The present invention relates to an amplifier driver circuit and, more particularly, to an operational amplifier driver circuit for supplying an undistorted ac signal to a resistive load connected across a balanced of twisted transmission lines on which substantial noise is present.
There are many applications, such as in telephony applications, in which it is desired to supply an undistorted ac voltage signal to a resistive load over balanced transmission lines such as twisted-pair transmission lines. The twisted-pair lines are often quite long, for example, two to three miles long, and are ordinarily subjected to substantial noise of an external, uncontrolled nature. The effect of this noise is to establish signals on the lines, commonly referred to as common mode signals, which, depending on the level of the common mode signals, cause the ac voltage appearing across the resistive load to be distorted or lost. The present invention is directed to a solution to the abovementioned problem.